EFFECT OF NANO-TiO₂ ON THE DURABILITY OF ULTRA-HIGH PERFORMANCE CONCRETE WITH AND WITHOUT A FLEXURAL LOAD

Abstract

In this study, the durability of nano-TiO₂ modified ultra-high performance concrete (UHPC) with and without a flexural load was experimentally investigated. Firstly, the mechanical properties of UHPC with various nano-TiO₂ contents were tested, and the results showed that UHPC with 1 wt% nano-TiO₂ exhibited the best mechanical properties. Then, 1wt% nano-TiO2 was added into UHPC to evaluate its effects on dry shrinkage, chloride ingress resistance, freeze-thaw resistance and carbonation resistance of UHPC. The effect of the flexural load on the durability of UHPC was also studied. The dry shrinkage of nano-TiO₂ modified UHPC was reduced compared with the control UHPC. The flexural load accelerated the chloride penetration process in the tensile region of the UHPC specimens, and the addition of nano-TiO₂ mitigated the negative influence of flexural load on the chloride ingress resistance of UHPC. Moreover, the addition of nano-TiO2 particles also improved the freeze-thaw resistance of the flexural loaded UHPC by reducing the mass loss under 800 freeze-thaw cycles. Carbonation was not detected in all UHPC specimens after being exposed to 60% CO₂ for 180 days. Furthermore, the MIP results indicated that the addition of nano-TiO₂ refined the pore structure of the UHPC, which improved the mechanical properties and durability of the UHPC.

Keywords

• Ultra-high performance concrete
• Nano-TiO₂
• Mechanical properties
• Durability
• Flexural load